The present invention relates to a switch assembly having diffused illumination.
An electronic device may use an illuminated switch assembly to permit a user to identify a switch during darkness or conditions of low ambient light. In one prior art configuration, an illuminated switch assembly may include a knob that has a transparent or translucent region that represents a symbol or a graphical form to provide a recognizable indicator of the knob during conditions of low ambient light. For example, the transparent or translucent region of the knob may be formed by a laser-etching process. However, internal the light source that is supposed to be incident upon the translucent region may be partially obscured or blocked by a shaft, which is connected to the knob. Accordingly, an illuminated form or symbol on a knob may not be uniformly illuminated because of the shadow or dimness created by the obstruction of the shaft with respect to the light source. Another problem with back-lighting a knob is that the distance between the illuminated face of the knob and the light source may be so great as to reduce the brightness of the illuminated symbol or graphical form so as to make the symbol or form illegible or otherwise difficult for a user to interpret.
In another prior art configuration, the switch assembly may be associated with a light pipe or light tunnel to provide ring of illumination around the base of a knob. The light pipe may not provide uniformly distributed light, unless multiple light sources are used. The light-pipe configuration tends to leave the shaft associated with the knob exposed to provide an adequate illumination around the base of the knob. An exposed shaft may detract from the aesthetic appearance of the switch assembly or the associated electronic device that uses the switch assembly. Moreover, the exposed shaft of the switch assembly may allow foreign particles, such as dirt or debris, to become lodged in the interior of the switch assembly or to interfere with the proper operation of an electronic device associated with the switch assembly. Reliable operation of the electronic device on the switch assembly may be compromised by electrically conductive or nonconductive particles entering about the region of the shaft. Conductive particles may cause electrical shorts for the electronic device, whereas nonconductive particles may interfere with the operation of electrical contacts, for example. Thus, a need exists for a switch assembly that is illuminated in a generally uniform manner to provide a reliable and intelligible identifier of the switch without sacrificing compactness. Further, a need exists for switch assembly that hides a shaft of the switch for enhanced aesthetic appearance or protect the reliable operation of the switch and its associated electronics.
In accordance with the invention, the switch assembly comprises a substrate and a multi-way switch mounted on the substrate. A knob is connected to the multi-way switch and has a perimeter. The knob is used for controlling a position (e.g., a shaft position) or corresponding electrical state of the multi-way switch. At least one light source is associated with the substrate. A light diffuser is located at least partially in an optical path between one or more of the light sources and a region about the perimeter of the knob.
The switch assembly provides uniformly dispersed light and protects an interior of the switch assembly from the ingress of foreign particles. The switch assembly is well-suited for hiding the shaft of a multi-way switch from a user even at a maximum angular tilt of the shaft of the multi-way switch.